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  • Title: The kinetic mechanism of inhibition of human leukocyte elastase by MR889, a new cyclic thiolic compound.
    Author: Baici A, Pelloso R, Hörler D.
    Journal: Biochem Pharmacol; 1990 Mar 01; 39(5):919-24. PubMed ID: 2310417.
    Abstract:
    The cyclic thiolic compound 2-[3-thiophencarboxythio]-N-[dihydro-2(3H)-thiophenone-3-il] - propionamide (MR889) was investigated as inhibitor of endopeptidases. The activity of bovine pancreatic alpha-chymotrypsin, human leukocyte cathepsin G and rabbit liver cathepsin B was not affected by MR889, whereas porcine pancreatic elastase and human leukocyte elastase were inhibited. The kinetic mechanism of inhibition of human leukocyte elastase was of the reversible, slow-binding, fully competitive type. The rate constants for complex formation between MR889 and leukocyte elastase, determined by pre-steady-state kinetic analysis in the presence of a tetrapeptide substrate at 37 degrees and pH 7.40, were kon = 2363 +/- 15 M-1 sec-1, koff = 3.01 +/- 0.34 x 10(-3) sec-1. The inhibition equilibrium constant was Ki = koff/kon = 1.27 +/- 0.15 microM. Ki, calculated from steady-state kinetic experiments, was 1.38 microM. MR889 also inhibited the elastolytic activity of leukocyte elastase, as determined with insoluble elastin as the substrate.
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